According to state television, 22,464 had been killed and another 41,054 were missing after cyclone Nargis barrelled into the low-lying Irrawaddy delta with 120mph winds, bringing with it an enormous storm surge that indunated towns and villages.

The social welfare minister Maung Maung Swe said that 95 per cent of houses in the delta town of Bogalay had been "destroyed".

"More deaths were caused by the tidal wave than the storm itself," he added. "The wave was up to 12 feet high and it swept away and inundated half the houses in low-lying villages. They did not have anywhere to flee."

If previous disasters of this kind are anything to go by, few of the missing are likely to be found alive, and if anything the toll could rise further. Around one million people were estimated to be homeless.

But despite the scale of the devastation, Burma's military junta — the country has been under a dictatorship for 46 years — were obstructing the entry of foreign aid personnel and supplies.

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"The United Nations is asking the Burmese government to open its doors. The Burmese government replies: 'Give us money, we'll distribute it.' We can't accept that," said the French foreign minister Bernard Kouchner, who is a co-founder of the aid agency Medecins Sans Frontieres.

A UN disaster assessment team was stuck in Thailand overnight, unable to obtain visas, and the Burmese embassy in Bangkok was closed on Monday for a Thai holiday.

Countries around the world are offering help, but have yet to be invited in by the authorities, and aid agencies say that their staff are still waiting for visas.

"Unfortunately we cannot tell you how many people are in need of assistance," he said. "We just clearly understand that it will probably be in the hundreds of thousands."

But if visas were not forthcoming there were few alternatives, he said. "The backup plan is to urge (the government) to issue visas."

Burma's rulers are deeply suspicious of the outside world, particularly the West, but after years of mismanagement, corruption and self-imposed economic isolation, the country's infrastructure is creaking at the best of times, and their ability to distribute huge quantities of supplies across a vast area in dire circumstances is highly questionable.

One aircraft arrived in Rangoon from Thailand with nine tonnes of food and medicine, but had to be unloaded by hand as no forklift trucks were available.

The World Food Programme began distributing 800 tons of food — a tiny amount relative to the scale of the disaster - in Rangoon, where supplies are running short, but its country director Chris Kaye said: "In order to meet the needs of the persons most badly affected by the disaster, much more cooperation will be required in the short term."

The military government said a constitutional referendum that is part of its so-called "roadmap to democracy" would go ahead this weekend, except in the worst-affected areas. Aung San Suu Kyi's opposition National League for Democracy, which won elections in 1990 but has never been allowed to take power, said the decision was "extremely unacceptable".

But analysts said the vote could give ordinary Burmese a safe way to protest against the generals' handling of the disaster, after their bloody crackdown on protesting monks and civilians last year.

"The juxtaposition of the cyclone and the voting might cause many in Burma to feel this is an indication that the military should not be in power," said David Steinberg, a Burma expert at Georgetown University in Washington.

Many Burmese are deeply traditionalist, he pointed out, and the disaster could be taken to mean the current rulers had lost the "mandate of heaven".

In Rangoon, where monks and civilians were clearing the streets of debris, a man who refused to be identified added: "Where are all those uniformed people who are always ready to beat civilians? They should come out in full force and help clean up the areas and restore electricity."